Clean rooms are used, for example, in pharmaceutical facilities to provide an atmosphere uncontaminated by dust, pollen, bacteria and the like for processing and packaging drugs and other pharmaceutical products. Clean rooms are also used in the food, aerospace and electronic industries as well as in hospitals to provide an uncontaminated atmosphere.
Typically, a clean room comprises a sealed enclosure to which air is supplied by an air circulating system. In order to remove airborne contaminants the air circulating system includes one or more filter assemblies which filter the air before it enters the clean room. The one or more filter assemblies are normally mounted in the ceiling or wall of the clean room or comprise a false ceiling which is suspended from the structural ceiling of the clean room. The filter assemblies to which this invention relates include a housing which is adapted to receive a suitable replaceable filter unit. The housing is connected by duct work or a plenum to a blower which forces air through the filter unit into the clean room.
Industry practice and government regulation have required increasingly stricter standards for clean room performance. It has been necessary in recent years to improve the design of clean rooms and particularly the air circulating system to improve and insure the quality of the air entering the clean room. One problem which has been difficult to overcome is that of sealing the air circulating system to prevent accidental introduction of contaminants into the clean room. For example, leaks may occur within the filter assembly which permit unfiltered air to bypass the filter unit and enter the clean room. Additionally, since many clean rooms are constructed using a number of filter assemblies, sealing problems arise between adjacent filter assemblies resulting in another source of contamination.
The instant invention provides a unique filter assembly having greatly improved sealing properties which reduce the possibility of internal leaks. The filter assembly is suitable for use in the construction of clean rooms or in the construction of controlled atmosphere bench units. The instant invention also provides a unique total clean room design incorporating a plurality of the filter assemblies which facilitates construction of the clean room and helps to prevent leaks between adjacent filter assemblies.